In view of the impact of harmonic torque on traction motors driven by frequency converters, the mechanism of harmonic torque on the copper squirrel cage rotor structure is analyzed. A combination of experimental and simulation methods is used in order to identify the characteristics at the rotor end of the squirrel cage. Firstly, modal analysis is conducted to obtain the modal parameters of the squirrel cage rotor. Then, a finite element model of the squirrel cage rotor based on the modal tests is established, and its static strength and harmonic dynamic response under 12 times of frequency-induced electromagnetic excitation are simulated and analyzed. Finally, based on the guide bar vibration test platform, the torsional vibration characteristics of the squirrel cage rotor end are investigated and the load amplification effect is verified, which provides certain theoretical support for improving the structural reliability of the copper squirrel cage rotor end.